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/*
* Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
* Copyright (C) 2006, Shawn O. Pearce <spearce@spearce.org>
* Copyright (C) 2008, Kevin Thompson <kevin.thompson@theautomaters.com>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* - Neither the name of the Git Development Community nor the
* names of its contributors may be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

using System;
using System.IO;

namespace GitSharp.Core
{
public class TreeIterator
{
private readonly Tree _tree;
private readonly Order _order;
private readonly bool _visitTreeNodes;

private int _index;
private TreeIterator _sub;
private bool _hasVisitedTree;

/// <summary>
/// Traversal order
/// </summary>
[Serializable]
public enum Order
{
/// <summary>
/// Visit node first, then leaves
/// </summary>
PREORDER,

/// <summary>
/// Visit leaves first, then node
/// </summary>
POSTORDER
};

/// <summary>
/// Construct a <see cref="TreeIterator"/> for visiting all non-tree nodes.
/// </summary>
/// <param name="start"></param>
public TreeIterator(Tree start)
: this(start, Order.PREORDER, false)
{
}

/// <summary>
/// Construct a <see cref="TreeIterator"/> for visiting all nodes in a
/// tree in a given order
/// </summary>
/// <param name="start">Root node</param>
/// <param name="order"><see cref="Order"/></param>
public TreeIterator(Tree start, Order order)
: this(start, order, true)
{
}

/// <summary>
/// Construct a <see cref="TreeIterator"/>.
/// </summary>
/// <param name="start">First node to visit</param>
/// <param name="order">Visitation <see cref="Order"/></param>
/// <param name="visitTreeNode">True to include tree node</param>
private TreeIterator(Tree start, Order order, bool visitTreeNode)
{
_tree = start;
_visitTreeNodes = visitTreeNode;
_index = -1;
_order = order;
if (!_visitTreeNodes)
{
_hasVisitedTree = true;
}

try
{
Step();
}
catch (IOException e)
{
throw new Exception(string.Empty, e);
}
}

private TreeEntry NextTreeEntry()
{
if (_sub != null)
return _sub.NextTreeEntry();

if (_index < 0 && _order == Order.PREORDER)
return _tree;

if (_order == Order.POSTORDER && _index == _tree.MemberCount)
return _tree;

if (_tree.Members.Length <= _index)
return null;

return _tree.Members[_index];
}

private bool HasNextTreeEntry()
{
if (_tree == null) return false;

return _sub != null || _index < _tree.MemberCount || _order == Order.POSTORDER && _index == _tree.MemberCount;
}

private bool Step()
{
if (_tree == null) return false;
if (_sub != null)
{
if (_sub.Step()) return true;
_sub = null;
}

if (_index < 0 && !_hasVisitedTree && _order == Order.PREORDER)
{
_hasVisitedTree = true;
return true;
}

while (++_index < _tree.MemberCount)
{
Tree e = (_tree.Members[_index] as Tree);
if (e != null)
{
_sub = new TreeIterator(e, _order, _visitTreeNodes);
if (_sub.HasNextTreeEntry()) return true;
_sub = null;
continue;
}
return true;
}

if (_index == _tree.MemberCount && !_hasVisitedTree && _order == Order.POSTORDER)
{
_hasVisitedTree = true;
return true;
}

return false;
}


public bool hasNext()
{
return HasNextTreeEntry();
}

public TreeEntry next()
{
TreeEntry ret = NextTreeEntry();
Step();
return ret;
}
}
}
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